AFM University Introduction to Atomic Force Microscopy by Paul West

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6.1 Probe Artifacts
6.1.1 Features on a Surface Appear Too Large
6.1.2 Features in an Image Appear Too Small
6.1.3 Strangely Shaped Objects
6.1.4 Repeating Strange Patterns in an Image
6.2 Scanner Artifacts
6.2.1 Probe / Sample Angle
6.2.2 X-Y Calibration / Linearity
6.2.3 Z Calibration / Linearity
6.2.4 Background Bow / Tilt
6.2.5 Z Edge Overshoot
6.2.6 Scanner Drift
6.2.7 X-Y Angle Measurements
6.2.8 Z Angle Measurements
6.3 Image Processing
6.3.1 Leveling
6.3.2 Low Pass Filter
6.3.3 Matrix Filter / Smoothing
6.3.4 Fourier Filtering
6.3.5 Image Looks Too Good
6.4 Vibrations
6.4.1 Floor Vibrations
6.4.2 Acoustic Vibrations
6.5 Other Sources
6.5.1 Surface Contamination
6.5.2 Electronics
6.5.3 Vacuum Leaks
6.5.4 PID Settings / Scan Rate
6.5.5 Laser Interference Patterns
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Chapter 6
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Artifacts from electronics most often appear as oscillations or unexplainable repeating patterns in an image. Electronic ground loops and broken components are usually the source of electronic noise.
FIGURE 6-27 Image of a test pattern that has electronic noise at the top and bottom of the scan. The electronic noise in this case was a result of not having a ground wire attached to the stage. The artifact is identified by the oscillations.
6.5.3 Vacuum Leaks
Atomic force microscopes that are designed for imaging wafers and discs often use a vacuum chuck to hold the wafer/disc while scanning images. A leak in the vacuum between the specimen holder and the specimen can cause image artifacts. The artifact causes a loss of resolution in the image. Cleaning the vacuum chuck and sample often eliminates this problem.
6.5.4 PID Settings / Scan Rate
If the PID Settings used while scanning are not optimized, there is a potential for an artifact being generated in an image. This is because the probe is not tracking the surface, and the cantilever is bending to pass over surface features. This artifact can be identified easily by monitoring the error signal. If the error signal is too large, then the probe is not correctly tracking the surface.

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